Displacement molding plastic articles

ABSTRACT

In accordance with the present invention, plasticized plastic material is confined within a chamber of variable volume, and part of the walls of the chamber are formed by a first mold part which is movable relative to the chamber. A gate opening in the first mold part is normally blocked by a movable blocking member. A second mold part is initially spaced from the first mold part and is moved into contact with the first mold part. There is a mold cavity in the mold parts. At the same time, the blocking member is moved out of the gate opening so that the mold cavity communicates with the plasticized material in the chamber. The first and second mold parts are then moved jointly to reduce the volume of the chamber and thereby inject plasticized material through the gate opening into the mold cavity. Next, the gate opening is closed by the blocking member. The mold parts and the blocking member are moved in the reverse direction to enlarge the chamber to its original volume, and then the first mold part and the blocking member are halted while the second mold part moves further in the reverse direction to its initial position to accommodate ejection of the molded article. In one embodiment, the second mold part includes two members defining the mold cavity, these members being separable to effect ejection of the molded article.

llite ties atent ll I I [541 DISPLACEMENT MOLDING PLASTIC Division ofSer. No. 679,109, Oct. 30, 1972, Pat. No. 3,590,114.

[52] [1.8. CI. ..425/245, 425/354, 425/252, I

425/351 [51] Int. Cl. ..B29f l/00 [58] Field ofSe arch ..l8/30 AM,30PA,30 RV,

18/30 NW, 18/30 QM, 30 QB, 30 QC, 30 QD, 30 QF, 30 Ql-I, 30 QP, 30 QQ,30 QT, 30 Q2 I [56] References Cited UNITED STATES PATENTS 3,071,8141/1963 Guggenheim ..18/30QQ 3,488,810 1/1970 Gellert ..18/30RVX FOREIGNPATENTS OR APPLICATIONS 8,322 1961 Japan ..l8/30 QP Primary Examiner-H.A. Kilby, Jr. Attorney-Philip M. Rice and W. A. Schaich 1 Aagfl, 972

In accordance with the present invention, plasticized plastic materialis confined within a chamber of variable volume, and part of the wallsof the chamber are formed by a first mold part which is movable relativeto the chamber. A gate opening in the first mold part is normallyblocked by a movable blocking member. A second mold part is initiallyspaced from the first mold part and is moved into contact with the firstmold part. There is a mold cavity in the mold parts. At the same time,the blocking member is moved out of the gate opening so that the moldcavity communicates with the plasticized material in the chamber. Thefirst and second mold parts are then moved jointly to reduce the volumeof the chamber and thereby inject plasticized material through the gateopening into the mold cavity. Next, the gate opening is closed by theblocking member. The mold parts and the blocking member are moved in thereverse direction to enlarge the chamber to its original volume, andthen the first mold part and the blocking member are halted while thesecond mold part moves further in the reverse direction to its initialposition to accommodate ejection of the molded article. In oneembodiment, the

ejection of the molded article.

4 Claims, 18 Drawing Figures DISPLACEMENT MOLDING PLASTIC ARTICLES Thisapplication is a division of application Ser. No. 679,109, filed Oct.30, I967.

BACKGROUND OF THE INVENTION is affected by injection speed, moldtemperature and melt temperature. If these three factors are not welladjusted to each other, surface delamination will occur. While filling amold, the incoming melt may stick to the wall of the mold cavity, andfurther filling proceeds through the core of the plastic on the wall ofthe cavity. If the temperature of the wall of the cavity is very low, orif filling speed is very slow, a pronounced boundary layer is formedwhich is no longer melted down or fused by the subsequently followingmaterial. It is recommended that the difference between temperature ofmelt and temperature of mold be as small as possible where the injectionspeed is relatively slow. If injection speed can be increased, thedanger of layer build-up as explained above will be reduced.

Many modern injection molding machines utilize reciprocating extruderswhich make it possible to inject plasticized material into a mold cavityat high speed and under high pressure. This in turn calls for very highmold clamping forces, all of which complicates the machinery and makesit more expensive. It is also very difficult to maintain a certaininjection pressure throughout the entire injection head system withoutcreating too much of a pressure drop through channelmg.

Another problem with modern fast injection molding machines involves thesmall filling gate used in such machines. When plastic melt is injectedunder high pressure through this small filling gate, friction producedby the melt passing through the gate produces heat which tends todegrade the plastic material.

SUMMARY OF THE INVENTION It is now proposed to overcome the foregoingproblems by utilizing a displacement molding principle in which movablemolds displace plasticized material from a chamber into a mold cavity atvery high filling speed. No expensive reciprocating extruder is neededbecause the displacement chamber can be filled with plasticized materialunder low pressure produced by an inexpensive extruder. A relativelylarge gate opening can be used to reduce frictionally induced heat.

The method and apparatus of the invention utilize a chamber of variablevolume which is filled with plasticized material supplied from aconventional extruder, and movable mold parts which are moved relativeto the chamber to reduce the volume of the chamber and thereby expressplasticized material into a mold cavity fonned by the mold parts. Theinvention utilizes the principles of a displacement molding method andapparatus described and claimed in US. Pat. No. 3,032,810 to L. D.Soubier and assigned to the present assignee. However, that patentinvolved injection, extrusion and blowing, and did not contemplateinjection of plasticized material into a cavity formed by separable moldparts.

In a particular embodiment of the present invention, part of the wallsof a displacement chamber are formed by one mold part which is movablerelative to the chamber. A second movable mold part is spaced from thefirst mold part. The first mold part has a gate opening through whichplasticized material may be injected into the mold cavity when it isformed, and this gate opening is initially closed by a blocking memberwhich may also form a portion of the walls of the mold chamber. Thesecond mold part is brought into contact with the first mold part, andat the same time the blocking member is moved out of the gate opening sothat the mold cavity communicates with the plasticized material in thedisplacement chamber. The first and second mold parts are then movedjointly to reduce the volume of the displacement chamber and therebyinject plasticized material through the gate opening into the moldcavity. After the injection step, the gate opening is closed by theblocking member. The mold parts and the blocking member are then movedin the reverse direction to return the displacement chamber to itsoriginal volume, and at this point the first mold part and the blockingmember are halted. The displacement chamber starts to fill up withplasticized material supplied from the extruder, and the second moldpart is moved further in the reverse direction to return it to itsinitial position spaced from the first mold part. The molded article isthe ejected from the mold.

The method and apparatus of the invention have several advantages. Themold cavity is filled very quickly, thus eliminating the problemsencountered with slow speed injection molding as explained above. Thisfast filling speed can be achieved inexpensively by the impact energy ofa moving mold part. No expensive reciprocating extruder is required. Asingle forward and reverse stroke of the mold accomplishes in thecorrect sequence: (1 gate opening (2) clamping of mold parts, (3) highspeed filling of cavities, (4) filling of displacement chamber, and (5ejection of container.

The cost of a machine of the proposed type is reduced by the followingfactors: (a) an inexpensive extruder can be used, (b) the cost ofhydraulic or mechanical equipment and control equipment for the singlestroke motion of the parts is low compared to existing machines, (c)less tooling is required as compared to existing machines, (d) fasttooling change is possible, (e) low maintenance cost is obtained, and(f) low labor cost is obtained.

It is, therefore, an object of the present invention to provide animproved method and apparatus for injection molding of plastic articlesby a displacement molding principle.

Another object of the invention is to provide a method wherein one stageof mold movement is used to form a mold cavity, and another stage ofmold movement is utilized to displace plasticized material into the moldcavity.

A further object of the invention is to provide molding apparatuswherein first and second mold parts cooperate with a gate blockingmember to fill a mold cavity by displacement of plasticized materialwith the molds, and to open and close a gate of the molds to allow suchfilling by a properly sequenced movement of the blocking member.

Another object of the invention is to fill a mold cavity by displacementmolding employing a single forward and reverse stroke of a mold memberwhich accomplishes 1 opening of a gate, (2) filling of a mold cavity bydisplacement molding, (3) re-closing of the gate, and (4) ejection ofthe molded article.

Other objects of this invention will appear in the following descriptionand appended claims, reference being had to the accompanying drawingsforming a part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

ON THE DRAWINGS FIGS. 1 through 4 are a series of views schematicallyillustrating the displacement molding method and apparatus of theinvention;

FIGS. 5 through 8 are a series of views showing one apparatus embodimentof the invention at various stages of a cycle and illustrating themethod steps of the invention;

FIGS. 9 through 12 illustrate another apparatus embodiment of theinvention at various stages of a cycle and also illustrate method steps;

FIG. 13 illustrates a modification of the embodiment of FIGS. 9 through12; and

FIGS. 14 through 18 illustrate a further apparatus embodiment of theinvention at various stages of a cycle and also illustrate method steps.

Before explaining the present invention in detail, it is to beunderstood that the invention is not limited in its application to thedetails of construction and arrangement of parts illustrated in theaccompanying drawings, since the invention is capable of otherembodiments and of being practiced or carried out in various way. Also,it is to be understood that the phraseology or terminology employedherein is for the purpose of description and not of limitation.

AS SHOWN ON THE DRAWINGS:

Referring first to FIGS. 1 through 4 inclusive, there is shown a base20, a lower mold member 22, an upper mold member 24 and a blockingplunger 26 at various positions in a cycle of operation to illustratethe nature of the method and apparatus of the invention. In FIG. 1, theupper mold part 24 is in a raised initial position spaced from the lowermold part 22 which is mounted for vertical movement within thecup-shaped base 20. A displacement chamber 28 is formed between thebottom of the lower mold part 22 and the inside bottom wall of the base20. The displacement chamber 28 communicates with a conventionalplasticizing extruder through an opening 30 in the side wall of the basemember 20, and plasticized material is supplied from the extruderthrough opening 30 to the displacement chamber 28 under relatively lowpressure.

The lower mold part 22 is also cup-shaped and has a recess 32 thereinwhich is adapted to receive a projecting male portion 34 of the uppermold part 24. Upper mold part 24 has a shoulder 36 which registers withand is adapted to engage the top rim 38 of the lower mold part 22.

There is a gate opening 40 through the bottom wall 42 of the lower moldpart 22, and this opening is normally closed by the reduced tip 44 ofthe blocking plunger 26. Blocking plunger 26 has a shoulder 46 whichseats on a registering surface of the lower mold part 22 when theblocking plunger 26 is in position to close the gate opening 40 as shownin FIG. 1.

With the various members of the apparatus in the positions shown in FIG.1, the displacement chamber 28 is filled with plasticized material, andthe gate opening 40 is closed by the plunger 26. The upper mold part 24is in an initial position spaced above the lower mold part 22.

The first step of the method is to move the upper mold part 24 intocontact with the lower mold part 22 so that the shoulder 36 of mold part24 abuts the rim surface 38 of the lower mold part 22 as shown in FIG.2. At the same time, the blocking plunger 26 is moved away from the gateopening 40 so that the mold cavity 50 formed between the upper and lowermold parts 24 and 22 communicates with the displacement chamber 28through the gate opening 40. The movement of the blocking plunger 26 maybe caused independently of the motion of the upper mold part 24, oralternatively, the upper mold part may be connected to the blockingplunger 26 so that the movement of the upper mold part forces theplunger 26 out of the gate opening.

The next step is to move the upper mold part 24 and the lower mold part22 jointly toward the body of plasticized material in the displacementchamber 28 so as to force plasticized material from the chamber throughthe gate opening 40 into the mold cavity 50. As shown in FIG. 3, thisreduces the volume of the displacement chamber 28 and fills the moldcavity 50 with plasticized material. During the joint motion of theupper mold part 24 and the lower mold part 22, the gate opening 40 isagain closed by the blocking plunger 26, also as shown in FIG. 3. Thejoint motion of the mold parts may continue until the lower mold part 22seats on the shoulder 46 of the blocking plunger 26, or alternatively,the blocking plunger 26 may be moved in the reverse direction until itseats against the lower mold member 22. It may be noted that during thejoint movement of the mold parts towards the displacement chamber 28,some excess plasticized material may be forced back through the opening30 into the extruder.

Next, the two mold parts 24 and 22 and the blocking plunger 26 are movedin the reverse direction to return the lower mold part 22 to its initialposition and to return the displacement chamber 28 to its originalvolume. The upper mold part 24 is moved in the reverse direction by ahydraulic cylinder or some other force applying means, and the lowermold part 22 is pushed back to its original position ky the blockingplunger 26. The blocking plunger 26 may be urged in the reversedirection by spring pressure or by hydraulic pressure or a mechanicaldrive.

When the displacement chamber 28 reaches its original volume, the lowermold part 22 and the plunger 26 are halted. The upper mold part 24continues to move in the reverse direction until it reaches its initialposition spaced above the lower mold part 22 as shown in FIG. 4. Theplastic article is carried by the upper mold part 24, and when the uppermold part reaches its initial position, the plastic article may beejected therefrom by a suitable ejector mechanism (not shown). While themold parts 22 and 24 are moving back to their initial positions, thedisplacement chamber 28 is filling up with plasticized material suppliedfrom the extruder through opening 30. When the displacement chamber 28is filled with plasticized material, the cycle is completed, and theapparatus is ready for the next molding cycle.

FIGS. 5 through 8 illustrate an embodiment of the invention in which ablocking plunger is moved in response to the motion of one of the moldparts. FIG. 5 shows the major parts of the apparatus of this embodiment.A movable platen 60 carries an upper mold part 62 (see FIG. 6), andplaten 60 is movable vertically on stationary guide posts 64 attached toan upper frame member 66 and a lower frame member 68. The latter framemember is mounted above a base 70 on supports 72, and in the spacebetween members 68 and 70 there is a multiple station compression head74 which includes a lower mold part 76 (see FIG. 6). The movable platen60 is raised and lowered by means of a hydraulic or pneumatic cylinder78 mounted on frame member 66 with its piston connected to the platen60.

Actually, several upper mold parts and several corresponding lower moldparts may be carried by the platen 60 and the compression head 74, andthe lower mold parts are represented by circles 80in FIG. 5. Pins 82 areprovided in association with the compression head 74 for moving theblocking plunger associated with each lower mold part, and the pins 82are actuated by other pins 84 carried by the movable platen 60.

Plasticized material is fed to displacement chambers in the compressionhead 74 from an extruder 86 which has a hopper 88 through which plasticmaterial is fed into the extruder. Extruder 86 is mounted on the base70.

Referring to FIG. 6, an upper mold part 62 is shown mounted on platen 60in a raised position above the lower mold part 76 which is attached to amovable structure 90. The stationary base of the apparatus includesthree plates 92, 94 and 96, the upper plate 92 being attached to theintermediate plate 94 by screws 98, and the lower plate 96 beingattached to the intermediate plate 94 by screws 100. A furtherstationary member 102 is threaded at 104 and screwed into matchingthreads on the lower plate 96 so that member 102 may be adjustedvertically relative to plate 96. A displacement chamber 106 is formedbetween lower mold part 76 and movable structure 90 on the upper sideand stationary member 102 on the lower side. The

displacement chamber 106 communicates with the extruder 86 through apassageway 108 provided between plates 94 and 96.

The lower mold part 76 has a gate opening 110 through its bottom wallwhich is normally closed by a blocking plunger 112 which has a reducedtip 114 fitting within the gate opening. Plunger 112 has a shoulder 116which seats against the lower mold part 76. An enlarged head 118 isattached to plunger 112 by a screw 120, and head 118 clamps a plate 122to the plunger. Plate 122 is connected to the pin 82 by means of head124 and screw 126. Pin 82 extends through plates 92, 94 and 96 and isfreely movable relative to the latter plates. The upper end of pin 82 isin alignment with the pin 84 carried by the platen 60. Pin 84 has a head128 which is urged downwardly by a spring 130 provided in a recess 132in platen 60.

Stationary member 102 has a counterbore surface 140 therein, and aradially enlarged head 142 on plunger 112 fits movably within thiscounterbore sur' face. A chamber 148 is formed within the stationarymember 102. This chamber may be filled with oil or other hydraulicliquid supplied through an opening 150 which extends through the capmember 144. The opening 150 may be connected to an accumulator forstoring oil under pressure which is not shown in the drawings. Theplunger 112 is free to move within the vertical limits of the chamber148, and it is urged upward to the position shown in FIG. 6 by the oilpressure within the chamber 148.

Movable structure connected to lower mold part 76 is urged to an initialposition by the plunger 112 as shown in FIG. 6. Movable structure 90 hasa flange 154 thereon which fits in a recess 156 in plate member 92 asshown. Thus, movable structure 90 and lower mold part 76 are free tomove within the limits or recess 156.

In connection with the movable platen 60, there is an ejector pin 158which extends through upper mold part 62 and also through platen 60.With the platen 60 in the raised position shown in FIG. 6, the ejectorpin 158 abuts against a fixed structure 160 which causes the ejector pinto project from the face of upper mold part 62. FIG. 6 shows an article162 being ejected from the upper mold part 62 by the ejector pin 158. Asuitable spring (not shown) may be provided for urging ejector pin 158to a retracted position.

FIG. 6 also shows the displacement chamber 106 being filled withplasticized material supplied through passageway 108 from the extruder86. When the displacement chamber 106 is filled with plasticizedmaterial the apparatus is ready to begin a new cycle of operation. Itmay be noted that the flow of plasticized material through thepassageway 108 is controlled by a control member 166 which projects intothe passageway 108. Control member 166 may be adjusted vertically tocontrol the crosssectional size of the passageway 108 to thereby controlthe rate of filling the displacement chamber 106, and also to restrictthe flow of plasticized material in the reverse direction throughpassageway 108 when the displacement chamber 106 is reduced in volume inthe operation of the apparatus. Reverse flow over flow control 166creates back pressure which increases the injection pressure and thusincreases the density of the molded article 162. Less back pressurewould fill the mold cavity only loosely.

It will be understood that the method of the invention is carried out bythe apparatus of FIGS. 6 through 8. In the first step of the method, theupper mold part 62 and the platen 60 are moved toward the lower moldpart 76. During this movement, the pin 84 carried by platen 60 contactsthe pi 82 carried by plates 92, 94 and 96 and forces pin 82 downwardly,thus retracting blocking plunger 112 out of the gate opening in thelower mold part 76. As shown in FIG. 7, the blocking plunger 112 movesdownward until the enlarged head 142 abuts against end cap 144. As theplaten 60 and upper mold part 62 continue moving downward, the pin 84compresses spring and thus allows relative movement of the platen 60 tocontinue.

As the platen 60 moves downward further, the upper mold part 62 contactsthe lower mold part 76 and then begins to push the lower mold part 76and movable structure 90 downward so that the two mold parts movejointly toward the displacement chamber 106. During this movement theflange 154 on movable structure 90 rides downward through the recess 156until it abuts against intermediate plate 94. The latter condition ofthe apparatus is shown in FIG. 8.

In the condition of the apparatus shown in FIG. 8, the displacementchamber 106 has been reduced in volume, thus forcing plasticizedmaterial through the gate opening 110 into the mold cavity formedbetween the two mold parts and the blocking plunger. Some plasticizedmaterial also flows back through passage 108 into the extruder. Thelower mold part 76 has at this stage seated on the shoulder 1 16 of theplunger 1 12 such that the gate opening 1 is again closed.

Next, the cylinder 78 (FIG. 5) starts to withdraw the platen 60 in thereverse direction so that the upper mold part 62 moves in the reversedirection. The oil pressure applied to enlarge head 142 through theopening 150 forces the plunger 112 to follow the upper mold part, andthe plunger in turn pushes the lower mold part 76 along with the uppermold part until the lower mold part returns to its initial position asshown in FIG. 6. At this point, the flange 154 abuts against platemember 92 so that lower mold part 76 cannot move any farther. Theblocking plunger 112 is also halted with the enlarged head 142 abuttingagainst the upper end of the chamber 148.

The platen 60 and the upper mold part 62 continue to move in the upwarddirection until they reach their initial position as shown in FIG. 6.The molded article is carried on the upper mold part 62, and as theplaten 60 approaches its initial position, the ejector pin 158 hitsstationary structure 160 and further movement of the platen causes theupper mold part 62 to withdraw from the plastic article so that thearticle is ejected as shown in FIG. 6.

FIG. 9 through 12 show another embodiment of the invention which isadapted for the molding of squeeze tubes. FIG. 9 shows the apparatus ina condition where an upper mold part 170 is moving downward towards alower mold part which is made of two pieces 172 and 174. The lower moldpart 172, 174 is movable vertically within a base which is made up ofmembers 176, 178 and 180. Base portion 178 is an annular sleeve whichhas a bore surface 182 wherein a stationary structure 184 is provided.There is a space between the outer perimeter of stationary structure 184and the bore surface 182, and plasticized material is supplied throughthis space from an extruder which is not shown. The lower mold part 172,174 is movable vertically within the bore surface 182 of the baseportion 178. A displacement chamber 186 is formed between an innersurface 188 of member 174 and the end surface 190 of the stationarystructure 184. Piece 174 of the lower mold part has a flange 192 192which fits in a recessed surface 194 of base member 180. Another flange196 of member 180 overlies the flange 192 of member 174 and forms a stopfor holding the lower mold part in its upper position.

The stationary structure 184 has a central recess 200 therein which theblocking plunger 202 is received. The blocking plunger 202 is received.The blocking plunger 202 extends upwardly up through the lower mold part172, 174 and provides one of the wall surfaces of a cavity 204 in whicha squeeze tube is to be molded.

The blocking plunger 202 is urged to an upper position by a spring 206,and in this upper position a shoulder 208 on the plunger abuts against acorresponding shoulder 210 on portion 174 of the lower mold part. Theshoulder 210 defines a gate opening through which plasticized materialmay be injected from the displacement chamber 186 to the mold cavity204. With the plunger 202 in its upper position as shown in FIG. 9, thegate opening 210 is closed by blocking plunger.

Upper mold part 170 carries a core pin 212 which projects from the lowerend of the upper mold part 170. Annular surface 214 of upper mold part170 is threaded, and an annular space 216 is formed between the core pin212 and the threaded surface 214. The neck of the squeeze tube is formedin this annular space 216.

In the condition of the apparatus as shown in FIG. 9, the core pin 212has just made contact with the upper end of the blocking plunger 202.Thus, the upper mold part 170 is shown as it is moving down toward thelower mold part 172, 174. As the upper mold part 170 continues to movedownward, the blocking plunger 202 is also moved downward relative tothe shoulder 210 of the portion 174 of the lower mold part, and thisopens the gate opening at shoulder 210 so that the mold cavity 204communicates with the displacement chamber 186. The upper mold partreaches a position where its surface 220 abuts against the upper surface222 of portion 172 of the lower mold part. Further downward movement ofupper mold part causes the lower mold part 172, 174 to also movedownwardly, thus reducing the volume of the displacement chamber 186 andforcing plasticized material into the cavity 204. The upper mold partand the lower mold part continue moving jointly downwardly until theflange 192 on lower mold part 174 abuts against the top of thestationary base portion 178. The apparatus is shown in this condition inFIG. 10.

Next, the upper mold part 1 is retracted in the reverse direction, andthe pressure exerted on blocking plunger 202 by the spring 206 causesthe blocking plunger to follow the upper part 170. The plunger 202 inits upward movement engages the shoulder 210 of portion 174 of the lowermold part and from this point on pushes the lower mold portion 174 alongwith it until the flange 192 abuts against the overlying flange 196 ofbase portion 180. At this point, the upward motion of lower mold part172, 174 and blocking plunger 202 is halted.

The upper mold part 170 continues to move upward and carries a finishedsqueeze tube 224 along with it until the squeeze tube is clear of thelower mold part. The tube is physically separated when shoulder 210abuts against the other shoulder 208. This condition of the apparatus isshown in FIG. 11.

As shown in FIG. 12, the upper mold part 170 is provided with two halveswhich are then separated laterally to release the squeeze tube 224 andthus ejects the squeeze tube from the mold.

As the upper mold part is moving upwards, the displacement chamber 186is filling with plasticized material supplied through passageway 182from an extruder (not shown). Thus, when the finished article 224 hasbeen ejected, the apparatus is ready to begin a new cycle of operation.

As shown in FIG. 13, heaters 226 and 228 maybe provided in members 172and 202 to heat the mold cavity 204, and a coolant passage 230 may beprovided in mold part 170 to cool the neck space 216. Thus, the uppermold part may be kept cool to facilitate rapid cooling of the neck ofthe article while permitting cavity 204 to be maintained at optimumtemperature for molding.

Another embodiment of the invention in which cooling of a mold may beutilized is illustrated in FIGS. 14-18. In this embodiment, an uppermold 300 is formed by a cup-shaped mold member 302 and another moldmember 302 having a projection 306 adapted to enter the recess 308 inmember 302 to form a mold cavity 310. A gate opening 312 is provided incupshaped member 302 to allow communication between the mold cavity 310and a displacement chamber as will be described. The entire upper mold300 is movable in the vertical direction, and mold members 302 and 304are separable.

Mold member 304 has a passageway including openings 314 through whichwater or some other cooling liquid may be circulated to keep the moldmember cool. Mold member 302 also has a passageway including openings116 through which water or other cooling liquid may be circulated tokeep the' mold member cool.

Below mold 300 is provided an injection head 320 in cluding a cup-likebase 322 in which vertically movable lower mold member 324 is provided.Mold member 324 has a gate opening at 326 extending through the same,and this opening is normally closed by a blocking member 328 which has ashoulder at 330 abutting against a lip 332 of mold member 324. Theblocking member 328 holds lower mold member 324 in spaced relation withthe bottom 334 of base 322 to form a displacement chamber 336, and thisdisplacement chamber communicates with a source of plasticized materialthrough an opening 338 in the side wall of base member 322.

Initially, the displacement chamber 336 is filled with plasticizedmaterial which has been supplied from the source thereof. In FIG. 14,the mold assembly 300 is shown with mold members 302 and 304 in contactwith each other to form the mold cavity 310, and mold 300 is in a raisedposition over the injection head 320. It will be understood, however,that mold member 304 may initially be spaced above mold member 302 andthen brought down into contact with mold member 302 to form the moldcavity 310.

Mold 300 is then lowered toward injection head 320 to bring mold member302 into contact with the lower mold member 324 which is a part of theinjection head, and to align gate opening 312 with gate opening 326.Then the blocking plunger 328 is lowered to move the tip of the blockingplunger out of gate opening 326 so that the mold cavity 310 communicateswith the displacement chamber 336 through gate openings 312 and 326. Thecondition of the apparatus at this stage is shown in FIG. 15.

Mold members 302, 304 and 324 are then lowered further towards thedisplacement chamber 336 to force plasticized material from thedisplacement chamber through gate openings 312 and 326 into the moldcavity 310 as the volume of the displacement chamber 336 is reduced. Themold members may be lowered until lip 340 of mold member 302 abutsagainst the top edge 342 of base 322 in the manner shown in FIG. 16. Atthis stage, displacement chamber 336 has been reduced to its minimumvolume, and gate openings 326 and 312 have slipped over the tip end ofblocking plunger 328 so that the gate openings are again closed by theblocking member.

Mold members 302, 304 and 324 are then raised jointly to return thedisplacement chamber to its original volume, and at this point moldmember 324 is halted. During this motion, mold member 324 may be raisedby the blocking plunger 328, whereas mold members 302 and 304 are raisedby a head (not shown) to which they are connected.

Mold members 302 and 304, still in contact with each other, are thenraised further away from mold member 324 until the lip 340 of moldmember 302 contacts an abutment 344 mounted in a stationary position ona support 346. The apparatus at this stage of the process is illustratedin FIG. 17. It may be seen that a plastic article 348 has been formed inthe mold cavity 310. Mold members 302 and 304 are in raised positionabove injection head 320, and the motion of mold member 302 has beenhalted by the abutment 344. Displacement chamber 336 is at its originalvolume and is again being filled with plasticized material supplied fromthe source thereof through opening 338.

Mold member 304 is then raised further to separate it from cup-shapedmold member 302 to the position shown in FIG. 18. The plastic article348 is carried by mold member 304, and at this stage the plastic article348 may be ejected from mold member 304 by any suitable means such as anejector plunger of the type used in the previous embodiments.

One important feature of the embodiment of FIGS. 14-18 is that the moldmembers 302 and 304 which form the mold cavity 310 may be kept cool bythe liquid circulated through passageways 314 and 316 to facilitaterapid cooling of the plastic article 348 after it has been formed. Theinjection head 320 including the mold part 324 may be kept hot by theplasticized material, perhaps supplemented by heating means if desired,to maintain the displacement chamber at an optimum temperature formolding. This affords a reduction in the cycle time as compared forexample in the embodiment of FIGS. 1 4 where one entire mold half ispart of the hot injection head.

Although the present invention has been described in connection with themolding of plasticized plastic material, the method and apparatusobviously could be utilized with any material capable of being molded.

Having thus, described my invention, I claim:

1. In an apparatus for making a plastic object, means including a firstmovable mold part defining a chamber of variable volume for containing abody of plasticized material, means for supplying plasticized materialto said chamber, a second movable mold part having an initial positionspaced from said first mold part, means for moving said second mold partin two stages toward said body of material l to bring said second moldpart into contact with said first mold part with said mold partsdefining a mold cavity, and (2 2) to move said first and second moldparts jointly in a first direction to reduce the volume of said chamberand thereby force plasticized material into said mold cavity, and meansfor moving said second mold part in the reverse of said first directionin two stages (1) to return said first and second mold parts topositions wherein said chamber is at the original volume thereof, and(2) to subsequently return said second mold part to said initialposition thereof, movable flow control means carried by said first moldpart and normally interposed between said chamber and said mold cavitywhen said mold parts are in contact, and means for moving said flowcontrol means to interconnect said chamber and said cavity only duringjoint movement of said mold parts in said first direction.

2. In an apparatus for making a plastic object by injection ofplasticized material into an injection mold, means including a firstmovable mold part defining a chamber of variable volume for containing abody of plasticized material, said first mold part having a gate openingtherein through which material may be injected from said body into acavity formed partly by said first mold part, a movable blocking meansnormally closing said gate opening, means for supplying plasticizedmaterial to said chamber, a second movable mold part having an initialposition spaced from said first mold part, means movable with saidsecond mold part engageable with said blocking means to move saidblocking means away from said gate opening to thereby open said gateopening, means for moving said second mold part in two stages towardssaid body of material (1) to bring said second mold part into contactwith said first mold part to thereby form a mold cavity and to move saidblocking means away from said gate opening so that said mold cavitycommunicates with said body of material through said gate opening, and(2) to move said first and second mold parts jointly in a firstdirection to reduce the volume of said chamber and thereby forceplasticized material through said gate opening into said mold cavity andultimately to close said gate opening with said blocking means, andmeans for moving said second mold part in the reverse of said firstdirection in two stages (1) to return said first and second mold partsand said blocking means to positions wherein said chamber is at theoriginal volume thereof, and (2) to subsequently return said second moldpart to said initial position thereof.

3. The apparatus for making plastic objects as claimed in claim 2 andfurther including ejection means with said second mold part actuatedupon return of said second mold part to said initial position thereof toeject said object from said second mold part.

4. The apparatus for making plastic objects as claimed in claim 2 inwhich said blocking means has a portion defining part of the walls ofsaid chamber.

1. In an apparatus for making a plastic object, means including a firstmovable mold part defining a chamber of variable volume for containing abody of plasticized material, means for supplying plasticized materialto said chamber, a second movable mold part having an initial positionspaced from said first mold part, means for moving said second mold partin two stages toward said body of material (1) to bring said second moldpart into contact with said first mold part with said mold partsdefining a mold cavity, and (2 2) to move said first and second moldparts jointly in a first direction to reduce the volume of said chamberand thereby force plasticized material into said mold cavity, means formoving said second mold part in the reverse of said first direction intwo stages (1) to return said first and second mold parts to positionswherein said chamber is at the original volume thereof, and (2) tosubsequently return said second mold part to said initial positionthereof, movable flow control means carried by said first mold part andnormally interposed between said chamber and said mold cavity when saidmold parts are in contact, and means for moving said flow control meansto interconnect said chamber and said cavity only during joint movementof said mold parts in said first direction.
 2. In an apparatus formaking a plastic object by injection of plasticized material into aninjection mold, means including a first movablE mold part defining achamber of variable volume for containing a body of plasticizedmaterial, said first mold part having a gate opening therein throughwhich material may be injected from said body into a cavity formedpartly by said first mold part, a movable blocking means normallyclosing said gate opening, means for supplying plasticized material tosaid chamber, a second movable mold part having an initial positionspaced from said first mold part, means movable with said second moldpart engageable with said blocking means to move said blocking meansaway from said gate opening to thereby open said gate opening, means formoving said second mold part in two stages towards said body of material(1) to bring said second mold part into contact with said first moldpart to thereby form a mold cavity and to move said blocking means awayfrom said gate opening so that said mold cavity communicates with saidbody of material through said gate opening, and (2) to move said firstand second mold parts jointly in a first direction to reduce the volumeof said chamber and thereby force plasticized material through said gateopening into said mold cavity and ultimately to close said gate openingwith said blocking means, and means for moving said second mold part inthe reverse of said first direction in two stages (1) to return saidfirst and second mold parts and said blocking means to positions whereinsaid chamber is at the original volume thereof, and (2) to subsequentlyreturn said second mold part to said initial position thereof.
 3. Theapparatus for making plastic objects as claimed in claim 2 and furtherincluding ejection means with said second mold part actuated upon returnof said second mold part to said initial position thereof to eject saidobject from said second mold part.
 4. The apparatus for making plasticobjects as claimed in claim 2 in which said blocking means has a portiondefining part of the walls of said chamber.